1. Field of the Invention
The present invention relates to a multilayer ceramic capacitor containing a dielectric ceramic material.
2. Description of the Related Art
In general, multilayer ceramic capacitors each include a ceramic main body and outer electrodes, as described in Japanese Unexamined Patent Application Publication No. 2008-081351. The ceramic main body includes two main surfaces opposite to each other, two side surfaces opposite to each other, and two end surfaces opposite to each other. The outer electrodes are provided on the two respective end surfaces of the ceramic main body.
The ceramic main body is a multilayer body that includes an inner layer portion and outer layer portions. The inner layer portion includes a plurality of ceramic layers for inner layers and a plurality of inner electrodes arranged at the interfaces between the plurality of ceramic layers for the inner layers. The outer layer portions include a plurality of ceramic layers for outer layers, the plurality of ceramic layers for the outer layers being arranged vertically so as to sandwich the inner layer portion. The inner electrodes are electrically connected to the outer electrodes.
With respect to multilayer ceramic capacitors, as trends toward a reduction in the thickness of individual ceramic layers and an increase in the number of ceramic layers progress, rare-earth elements are often added in order to stabilize the temperature characteristics of capacitance and to ensure the high-temperature load life over the long term in terms of insulation resistance.
Rare-earth elements, however, tend to concentrate at ceramic boundaries or segregated phases. Rare-earth elements are easily eluted in a water-soluble flux. Thus, resistance to elution in the water-soluble flux is disadvantageously reduced.
For this reason, in the case where such a multilayer ceramic capacitor is mounted, a ceramic component can be eluted in an organic acid contained in a water-soluble flux used for soldering. A ceramic main body includes inner electrodes (metal) and a ceramic material having a different linear thermal expansion coefficient from that of the inner electrodes, thus resulting in residual stress. The inner electrodes are two-dimensionally supported by outer layer portions. Thus, the outer layer portions receive relatively high residual stress, compared to portions of the ceramic main body at which the inner electrodes are not located, the portions of the ceramic main body being adjacent to both side surfaces of the ceramic main body on each of the ceramic layers for the inner layers. Accordingly, in the case where a component in the outer layer portions is eluted in the water-soluble flux to embrittle the outer layer portions, changes that occur over time after solder mounting disadvantageously cause a structural defect.